Question: $f(x) = -7x^2+8x+2 $ What is the value of the discriminant of $f$ ?
Answer: The ${\text{discriminant}}$ is a part of the quadratic formula. The sign of the discriminant tells us whether there are two roots, one root, or no roots. $\dfrac{-b\pm{\sqrt{\overbrace{{b^2-4ac}}^{\text{discriminant}}}}}{2a}$ Discriminant Roots Positive Two real roots Zero One repeated real root Negative No real root Let's find the discriminant of $f$ : $\begin{aligned} {b^2-4ac}&=8^2-4\cdot(-7)\cdot2 \\\\ &=64+56 \\\\ &={120} \end{aligned}$ So how many $x$ -intercepts does the graph of $f$ have? Since the discriminant is positive, the graph of $f$ has $2$ distinct $x$ -intercepts. In conclusion: The discriminant of $f$ is ${120}$. The graph of $f$ has $2$ distinct $x$ -intercepts.